Functionally-graded materials and the engineering of tribological resistance at surfaces

Abstract

An article is provided that is highly resistant to localized normal indentation, or indentation tensile stresses, against its surface. The article is a stacked array of at least five layer units each having local anisotropy in at least one direction. Each unit has an adjacent unit that differs in a mechanical property, or offset in principle axis of anisotropy by less than 45°. The article forms part of a construction constructed and positioned to withstand indentation, or contact damage, detrimental to its use having a component normal to any tangent of the surface. The article can be a stacked array of fiber-reinforced polymeric material, i.e., prepreg, with the fiber direction offset from each layer to the next by less than 45°. Methods of making the article and methods of use of the article to resist impact are provided. Also provided are articles having surfaces, the surfaces being constructed and arranged to withstand sliding contact stress. The surfaces of these articles are functionally-graded.

What is claimed is:  
     
       1. An article for resisting indentation against its surface, comprising: a stacked array, having a surface, of at least five layer units each having a principle axis of anisotropy, each unit having an adjacent unit and the principle axis of anisotropy of each unit being offset from that of a unit to which it is adjacent by less than 45°, wherein the offset in principle axis of anisotropy of each succeeding layer differs consistently in offset direction from each preceding layer, the article forming part of a construction constructed and positioned to withstand indentation having a component normal to a tangent of the surface. 
     
     
       2. An article as in  claim 1 , wherein the stacked array is a laminate composite. 
     
     
       3. An article as in  claim 1 , wherein the stacked array is an array of essentially linear, parallel fibers imbedded in a matrix, each unit having an adjacent unit offset in principle axis of anisotropy by less than 45°. 
     
     
       4. An article as in  claim 3 , wherein the stacked array is an array of stacked fiber-reinforced polymeric plies. 
     
     
       5. An article as in  claim 4 , wherein the stacked array is an array of stacked carbon fiber-reinforced polymeric plies. 
     
     
       6. An article as in  claim 5 , wherein the stacked array is an array of stacked fiber-reinforced epoxy plies. 
     
     
       7. An article as in  claim 2 , wherein the stacked array is an array of stacked fiber-reinforced epoxy plies. 
     
     
       8. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 35°. 
     
     
       9. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 25°. 
     
     
       10. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 20°. 
     
     
       11. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 15°. 
     
     
       12. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 12°. 
     
     
       13. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 8°. 
     
     
       14. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 6°. 
     
     
       15. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 4°. 
     
     
       16. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than about 2°. 
     
     
       17. An article as in  claim 16 , wherein the stacked array includes at least six layer units. 
     
     
       18. An article as in  claim 12 , wherein the stacked array includes at least eight layer units. 
     
     
       19. An article as in  claim 3 , wherein the stacked array includes at least ten layer units. 
     
     
       20. An articles as in  claim 17 , wherein the offset in principle axis of anisotropy of the units rotates through at least 90° through the stacked array. 
     
     
       21. An article as in  claim 3 , wherein the offset in principle axis of anisotropy of the units rotates through at least 90° through the stacked array. 
     
     
       22. An article as in  claim 16 , wherein the offset in principle axis of anisotropy of the units rotates through at least 90° through the stacked array. 
     
     
       23. An article as in  claim 2 , wherein the offset in principle axis of anisotropy of the units rotates through at least 90° through the stacked array. 
     
     
       24. An article as in  claim 1 , wherein the offset in principle axis of anisotropy of the units rotates through at least 90° through the stacked array. 
     
     
       25. An article as in  claim 24 , constructed and positioned to withstand an indentation having a component normal to a tangent of the surface of at least ⅕ the tangential force tolerable without failure of the construction. 
     
     
       26. An article as in  claim 19 , constructed and positioned to withstand an indentation having a component normal to a tangent of the surface of at least ⅕ the tangential force tolerable without failure of the construction. 
     
     
       27. An article as in  claim 16 , constructed and positioned to withstand an indentation having a component normal to a tangent of the surface of at least ⅕ the tangential force tolerable without failure of the construction. 
     
     
       28. An article as in  claim 25 , including instructions for use of the article to withstand an impact having a component normal to a tangent of the surface. 
     
     
       29. An article as in  claim 22 , including instructions for use of the article to withstand an impact having a component normal to a tangent of the surface. 
     
     
       30. An article as in  claim 16 , including instructions for use of the article to withstand indentation having a component normal to a tangent of the surface. 
     
     
       31. An article as in  claim 1 , wherein the stacked array includes at least six layer units. 
     
     
       32. An article as in  claim 1 , wherein the stacked array includes at least seven layer units. 
     
     
       33. An article as in  claim 1 , wherein the stacked array includes at least eight layer units. 
     
     
       34. An article as in  claim 1 , wherein the stacked array includes at least nine layer units. 
     
     
       35. An article as in  claim 1 , wherein the stacked array includes at least ten layer units. 
     
     
       36. An article as in  claim 1 , constructed and positioned to withstand indentation having a component normal to a tangent of the surface of at least ⅕ the tangential force tolerable without failure of the construction. 
     
     
       37. An article in  claim 1 , wherein the stacked array is constructed and positioned to withstand indentation by an indentor having a contact radius, and the layer units each have a thickness less than ⅕ the contact radius of the indentor. 
     
     
       38. An article in  claim 30 , wherein the stacked array is constructed and positioned to withstand indentation by an indentor having a contact radius, and the layer units each have a thickness less than ⅕ the contact radius of the indentor. 
     
     
       39. An article in  claim 22 , wherein the stacked array is constructed and positioned to withstand indentation by an indentor having a contact radius, and the layer units each have a thickness less than ⅕ the contact radius of the indentor. 
     
     
       40. An article in  claim 16 , wherein the stacked array is constructed and positioned to withstand indentation by an indentor having a contact radius, and the layer units each have a thickness less than ⅕ the contact radius of the indentor. 
     
     
       41. An article in  claim 1 , including instructions for use of the article to withstand indentation having a component normal to a tangent of the surface. 
     
     
       42. An article as in  claim 1 , wherein each layer unit comprises an oriented polymer having an offset in principle axis of anisotropic essentially perpendicular to a direction of orientation. 
     
     
       43. An article as in  claim 1 , each layer unit including reinforcing elements arranged to define an offset in principle axis of anisotropy, the offset in principle axis of anisotropy of each unit differing from each adjacent unit by less than 45°. 
     
     
       44. An article as in  claim 1 , wherein the construction exhibits Young's modulus at the surface of at least about 1 GPa. 
     
     
       45. An article as in  claim 1 , wherein each unit has an adjacent unit offset in principle axis of anisotropy by less than 25°, the offset in principle axis of anisotropy of each succeeding layer differing consistently in offset direction from each preceding layer and the offset in principle axis of an anisotropy of the units rotating through at least 90° through the stacked array, wherein the article is constructed and positioned to withstand indentation having a component normal to a tangent of the surface of at least {fraction (1/10)} the tangential force tolerable without failure of the construction by an indentor having a potential contact radius at least five times the thickness of each layer unit. 
     
     
       46. An article as in  claim 45 , wherein the stacked array is an array of stacked fiber-reinforced polymeric plies. 
     
     
       47. An article as in  claim 45 , wherein the article is a stacked array of iron-containing reinforcing rod-supported material. 
     
     
       48. An article as in  claim 1 , wherein the construction is a vehicle support surface. 
     
     
       49. An article as in  claim 48 , wherein the construction is a road bed. 
     
     
       50. An article as in  claim 1 , wherein the construction is an aircraft runway. 
     
     
       51. An article as in  claim 1 , wherein the construction is an automobile component. 
     
     
       52. An article as in  claim 1 , wherein the construction is a ship component. 
     
     
       53. An article as in  claim 1 , wherein the construction is a bulletproof object. 
     
     
       54. An article as in  claim 1 , wherein the construction is an armor component. 
     
     
       55. An article as in  claim 43 , wherein the reinforcing elements are iron-containing reinforcing rods. 
     
     
       56. An article as in  claim 55 , each layer unit comprising iron-containing reinforcing rod-supported concrete.